This invention relates to hand stamps and more particularly to a self-inking hand stamp that has a stamp holder with a pre-inked cartridge mounted in the stamp that inks the image forming stamp material. This invention also relates to the design and manufacture of the die box that holds the stamp forming material and pre-inked cartridge.
Most conventional stamps require manufacturing a stamping member from rubber or other flexible material. The stamping member is mounted on a handle that is grasped by the user. The stamping member is placed into contact with ink, usually contained in an inkpad. The inked stamping member is then pressed against the surface onto which the stamp image is to be transferred. Repetition of the stamping process required that the stamping member be pressed against the inkpad each time an image is to be transferred. This is a disadvantage to the user as it requires extra time for each re-inking step and slows down the stamping process if many stampings are to be done. It also requires the use of a separate inkpad that must be periodically re-inked.
An improved stamp was developed that uses a stamping member made from a permeable material that allows ink to pass through the stamping member. The ink is held within the stamp and allowed to gradually ooze onto the stamping member. This eliminated the need for a separate stamp inkpad. These stamps are referred to as self-inking stamps.
An example of this stamp is illustrated in U.S. Pat. No. 5,577,444 issued to Toyama. This patent illustrates a hand stamp that has a sealed ink compartment that stores the ink. The ink can be refilled into the compartment by means of removing a threaded screw at the top of the compartment. Once the screw is removed, the ink can be injected, and the screw replaced. The stamping member has a stamping surface with stamping and non-stamping portions.
There are several problems with this device. First it requires adding ink through the top to fill or refill the ink chamber. This is a messy procedure. It also may result in adding too little or too much ink to the ink chamber. Second, the chamber must be sealed to allow the ink to only ooze out through the bottom opening onto the stamp pad. Third, the stamp must be kept in its holder when not in use to protect the stamp surface as there is no guard that automatically drops down when the stamp is not pressed onto a stamp receiving surface to keep the stamping surface above the image receiving surface.
Another problem with this stamp is that it continually feeds ink to the entire stamp surface. The recessed portions that are not designed to contact the printing surface still have ink applied to them. This ink evaporates or dries and is wasted ink. The only ink that is needed for printing is the ink applied to the printing portions where the raised letters are located.
Another type of stamp pad is illustrated in U.S. Pat. No. 5,942,312 issued to Venkataraman et al. This patent discloses a pre-inked thermoplastic foam which has open cells in the area that is designed to transfer ink and closed or sealed cells in the area which is designed to be impermeable to ink. The inkpad is pre-inked before the image is formed on the thermoplastic material. Thus if there is a problem with the image, the entire pad including the ink, is wasted. Furthermore there may be difficulties in forming an image on a pre-inked pad as it may be messy or require special handling due to the ink in the pad.
U.S. Pat. No. 5,996,493 issued to Okumura et al. illustrates a hand stamp that uses an ink pack to supply ink to the porous stamp. The ink pack ruptures when the ink pack is pressed against a cutting device in the stamp. There is a transparent film thermally attached to the stamp surface to protect the stamp surface during transport and storage. The transparent film is removed just before using the stamp for printing images.
Another stamp is disclosed in U.S. Pat. No. 6,164,202 issued to Takami. This patent discloses a stamp unit comprising a holder, which is placed in a stamp manufacturing device for making a stamping surface on a stamp material. The holder interacts with the stamp manufacturing device to properly position the holder in the manufacturing device. The stamp forming material has a positive image or manuscript placed against the stamp forming material. The stamp forming material is irradiated with a xenon light. The part of the material irradiated with the light fuses due to the heating effect of the light. The part of the material not irradiated due to the characters on the manuscript is not fused and remains porous. This forms the image to be printed. The stamp forming material is saturated with ink and ink is allowed to flow out from the non fused portions onto a printing sheet forming the image. This patent describes the method and apparatus to form the stamp image on the stamp forming material and the disclosure is incorporated herein by reference.
The prior art devices do not adequately address the problem of conveniently inking the stamp forming material in a self inking hand stamp. For example U.S. Pat. No. 5,996,493 uses an ink pack that is placed in the stamp and is pierced by a cutting device to disburse the ink. Other self inking hand stamps use an ink cartridge stored in a sealed plastic bag. When the stamp material is ready to be inked, the sealed plastic bag is cut and the ink cartridge is carefully inserted into the stamp, generally in contact with the stamp forming material. To minimize the likelihood of ink getting on the user, a grasping tool such as a tweezers may be used to insert the ink cartridge into the stamp. This is not a convenient method of inking the stamp forming material in self-inking hand stamps. Another problem not solved by the prior art devices is providing an ink cartridge and stamp in a self contained easy to use unit. Also, the method of manufacturing such as unit was never taught.
Applicant addressed and solved many of the problems of the prior art devices as disclosed in its co-pending application. The co-pending application disclosed a container or stamp die box designed for insertion into a hand stamp. The hand stamp has a handle, which is grasped by the user. A stamping member is made of a stamp forming material that is a porous foam material and has a surface made of a porous resin layer. This is the image forming side of the stamping member. A pre-inked ink cartridge is placed adjacent to the side of the stamp forming material opposite the image forming side, but separated by an impermeable plastic film. The stamp forming material, ink cartridge and plastic film are retained in the die box and placed in a stamp forming machine to form the desired image on the image forming side of the stamp forming material. The porous resin layer is melted and solidifies into impermeable areas that are not intended to allow the passage of ink, and the porous resin layer remains unmelted and open in areas that are intended to allow ink to pass. In this manner the stamping image is defined. The ink cartridge is held against the plastic film, which in turn is in intimate contact with the backside of the stamp forming member. The die box is inserted into the hand stamp. When the stamp is ready to be used, the ink impermeable plastic film is pulled out from the die box. This allows the ink from the ink cartridge to flow into the stamp forming material. Once the stamp forming material is adequately saturated, the stamp is ready for use.
One shortcoming of Applicant's the invention in the co-pending application is that when the ink impermeable plastic film is pulled out from the die box, an air gap forms between at least a portion of the ink cartridge and the stamp forming material. This air gap slows the flow of ink from the ink cartridge to the stamp forming material, which lengthens the time before the stamp can be used once the impermeable plastic film is withdrawn from the die box.
In order to solve this problem, Applicant has discovered that placing a flexible, easily compressible, ink permeable rubber or foam material between the ink cartridge and the stamp forming material, eliminates the air gap and increases the flow rate of the ink from the ink cartridge to the stamp forming material when the ink impermeable plastic film is removed from the die box.
The die box is manufactured by placing the stamp forming material in the die box, covering it with the plastic film, placing a frame member around the perimeter of the inside of the die box, inserting an ink cartridge into the frame member, placing ink onto the cartridge, inserting a spacer into the die box, and closing the die box.